Just tried a quick speed test with the ESP8266. The ESP8266 is using Arduino, connected to the camera (CmuCam5) using SPI and sending data to my PC wwith Websockets (throug a router).
I have made a loop on the ESP8266 sending a counter (a 10 bytes char) to my PC. It is not getting any data from the camera right now.
Result : it sends data at 82 FPS
Same as before, but I am getting data from the camera and parse it in each loop.
Result : 42 FPS
As the camera is limited by its 50 FPS speed, it looks like the transmission delay is not that bad !